Detection of fluid movement in wells



1954 D. G. HARTWEG DETECTION OF FLUID MOVEMENT IN WELLS Filed June 17,1952 INVENTOR 00/6 6? Har/u/eg BY U z g if ATTORNEYS Feb. 23, 1954 FiledJune 17, 1952 D. G. HARTWEG DETECTION OF FLUID MOVEMENT IN WELLS 2Sheets-Sheet 2 INVENTOR Da/e 6. Herr/W619 BY x 14 ATTORNEYS PatentedFeb. 23, 1954 UNITED s t-Ares PATENT 'OEFLIFICEfiETECTION'"CDFFIjiffhiZVEMENTINWELIS Dow 'fihemieafidomlaany,=Midland;Michaya corporatinn (if-Delaware "Kpbfical tiiih mine 17, 1952-, Sefial"No. 293961 "3Ola'ims. (Cl. a e- 155) he apparatus finds its greatestfiis'efumes's. Lodating each "zones 'iseffe'cted witlr fihe a'ppara tusby' sensing and comparin fluiw'movement in the Well holefat-fvarioflsdepths am "ascertaining the depth "or "level 'at which the fluid*mov'ement snpws pronounced changes.

For s'e'rfsi'ngfiuid movement; there -is *s'uspended in the "fluid "onamablehaving a single i-h- 'sfiTatedwondnctor-in a balanced electricalcir- (itit, a' pair of electricallyheated thei'mallysensitive resistanceelements, the resistivity or one of *which changes "at a grea ter'ratethan-that of the other with a "change in temperature bi 'ought about *bymoveme'nt of :fiu'idi'n Contact with the resistance elements. Means an;br'otiided abeve gra mar supplying tc-'e'ach of the thermally sensitiveresistance elements "alternately "one or "the half waves, "respectively;df-an A. 0., a's'the heating current; th'rdngh the insulated conduc-"tdf and detecting-'2; difieience in the resistance of thse resistalhceelements, as a result of movernnt of fiuid--in"contact with them, as anunbalance in the said "balanced circuit.

msofer as Tam awarano apparatus =h'eretofore ava ilable h'as fully 'metthe problem "of locatingflfiiiid movement-inearth wells. Accordingly,theibri-mipalbbject of *the invention is toxprovide anapparettusfulfillingthis nee'd. This-eandother objectskvilkbecohueapparent as the description Ofithfl" invention 'proc'eeds. In connectionwith the description,"reference isflmade to the accompanying drawingillustrating by way ofexample various embodiments of: the inventionincluding aiprefei redembodiment.

''Referring 'to the drawing; Fig. 1*shovvs the complete apparatus partlyin diagrammatic term-with; anembodiment of the subsurfacaportionvof the=apparatus-largelyim section suspende'd by the-rcable .in the lzzc'maofawell, im osition to detcteornsense fiuidemovemenwa-nd the:aboveisin'ascertaining the location of these-that if round pertion 6fthe -appamaltizs which anal-aces the source of electi icity and providesthe ind?- "cationsoffluid mdvemehbahd the defithat' -wHiGh the'indications of the movement are "obtained.

Fig "isa =side elevation dargely i-n section o? 'a. modifi'a'tiohoff'the subsurface pcv'itioh 0f the anparawsof Fig; 1.

Figs; 3 *is' a side elevation largely in section of a prefel-"redntiodificatibn of the subs'ii'rfabe portion 6f the apparatus-of "Fig. 1.

Referring to the 'dT-aWi-hg in'dtaii-l, ther e i's 'shbwna; wen b01 9traversing athief 'zdne l-i n an earth formation 3. The u fiperpoitic'rr of the here is provided with =a casing *4 cemented in placewith 'the cetnent -sheath 5. A "pipe were nebtio'n 6 is'protiided forthe' intrddtietien of a cireiilation "fluid; siloh a's a rig mud f ro'ma "suitable source not shown, orm a mud co'l uinn Tinthe Well; Theforegemgwen 'str uctures are cnvemibnal and form 110 138 1 1: Of 'EhE'jpi BSGI'I't invi'itien.

'Th'euitiper ehe'ofwe-cab1e-mayjberun--were pulley l'9aboveth'ewellandthreaded thiofigha manage ifid'iat'or 2 'for measuring the IIfEfh of$153116. "Oiit "or "witl idiawri Tioin" the Well w'iththe "aid o'f'the''reel 2! on which the cable may be wound. As shown, the "r'el isproxii'l'ed with a turning crank 22 anti a pair of slip' nings 2 3 and24, the inner one-23-of which is-connected to; the insulated conductor"H} 0 5 the calblewand the.outer-one flM-to= 'the-=cab1e sheath *9andkmay baalso "connected: +10 ground: 2v5 -as indicated in 3 Fig. 1through the collector brush 26 which rides on slip ring 24.

The surface electrical equipment comprises means to indicate D. C.,.such as a D. C. milliammeter 21, one terminal of which is connected tothe collector brush 28 which rides on slip ring 23. The position of restof the pointer 23 of milliammeter 21, when there is no current flowthrough it, is at the center of the scale allowing the pointer todeflect to one side of center for a positive direct current and to theother side for a negative direct current. A condenser 30 having asuitable capacity, such as 500 mfd., may be shunted across themilliammeter as indicated in dotted lines, if desired. The other side ofthe milliammeter is connected to the slider 3| of a potentiometer 32 orvoltage divider. The voltage divider may have a resistance of 100' ohms,for example, from end to end. One end of the potentiometer is connectedto the negative terminal of a half-wave rectifier 33, such as a seleniumrectifier or vacuum tube rectifier capable of handling up to 400milliamperes, although rectifiers of other capacities and types may beused. The other end of the potentiometer is connected to the positiveterminal of a similar rectifier 34. The positive terminal of rectifier33 is connected to the negative terminal of rectifier 34 and to one sideof an A. C. milliammeter 35. The other side of the milliammeter isconnected to a grounded source of adjustable A. C. As shown, this maycomprise the slider 36 of an adjustable auto-transformer 31 having oneend of its winding connected to ground 25 and the other to one terminalof a suitable A. '0. generator 38, such as a 115 volt A. C. 60 cyclegenerator, the other terminal of which is connected to ground 25.

Referring to the case M of the subsurface portion of the apparatus,there is shown, in each of the three modifications of Figs. 1, 2, and 3,a pair of resistance elements 39 and 40 mounted on and insulated fromthe case II in a position to be contacted by the fluid, the movement ofwhich relative to the resistances is to be detected.

These resistances, as already indicated, have unequal heat dissipationcharacteristics, as by forming them of wires having preferablysubstantially equal electrical resistances but different surface areas.Equal electrical resistance and unequal heat dissipation may be achievedby making one of them, e. g. 39, of a short thin wire and the other, e.g. 40, of a longer thicker wire. For example, one of them may be of aninch of 40 gauge (American wire gauge) and the other inches of 32 gaugeboth of nickel wire. Such resistance elements have a resistance of 0.44ohm each. Resistance wire of other metals and sizes may be used. Theseresistance elements are mounted preferably parallel to each other andspaced apart preferably at least 0.03 inch on the outer surface of thecase. In general, 0.25 inch spacing is satisfactory, although a spacingof up to several inches may be used. Mounted internally of the case M isa pair of half-wave rectifiers 4| and 42, preferably of the seleniumtype. The positive terminal of rectifier 4| is connected to the negativeterminal of rectifier 42 and to the lowerend l8 of the insulatedconductor 10.

In the modification of the subsurface portion of the apparatus shown inFig. 1, one end of the shorter element, 39, is connected to the negativeterminal of rectifier 4| and the other end of the shorter element 39 isgrounded on the case M and'thereby connected to the sheath 9 of the 4-cable. One end of the longer element 40 is connected to the positiveterminal of rectifier 42 and the other end is grounded on the case andis thereby also connected to the cable sheath 9.

In the modification shown in Fig. 2, in addition to the pair ofhalf-wave rectifiers 4| and 42, there is included in the case M a pairof transformers 43 and 44 by which the rectifiers are coupled to theelements 39 and 40, respectively. The transformers may be similar to theordinary vacuum tube filament transformers in which the primaries aredesigned for operation at volt 50-60 cycle A. C. (a frequencycorresponding to ,thatof the A. C. source 38) and the secondaries at 2.5volts, although other transformers may be used. As shown, one of theterminals or the primary side of each of the transformers 43 and 44 isgrounded to the case M. The ungrounded primary terminal of transformer43 is connected to the negative terminal of the rectifier 3|, while theungrounded primary of the transformer 44 is connected to the positiveterminal of the rectiiier 42. The secondary of transformer 43 isconnected across the shorter element 39 and the secondary of transformer44 is connected across the longer element 40. The secondaries havecenter taps 45 and 46, respectively, which are preferably grounded.

In the modification of Fig. 3, the case M contains the same rectifiers,4| and 42, and transformers, 43 and 44, as the modification of Fig. 2with the addition of condensers 4'i and 48 shunted across the primary ofeach of the transformers 43 and 44, respectively As is manifest from thewiring diagram, when A. C. is supplied to the auto-transformer 31, therectifiers 33 and 34 allow the positive components or pulses of the A.C. to flow only through one of the branches, e. g. 49, of thepotentiometer 32, and the negative component or pulses of the A. C. onlythrough the other branch, e. g. 50. Similarly, the rectifiers 4| and 42allow only the positive pulses of the A. C. to pass through one of theelements, e. g. 4%, and the negative pulses of the A. C. pass onlythrough the other element, e. g. at. Since the positive and negativepulses of the A. C. follow in quick succession, at a rate determined bythe frequency of the A. C. source 30, the pointer 23} merely indicates,in effect, the ratio of the magnitude of one kind of pulse relative tothat of the other passing through one branch of the potentiometer 32relative to the other branch. At the position of rest of the pointer 29,there is either no current flow at all, as aforesaid, or the magnitudeof the positive pulses is equal to that of the negative pulses. Shouldthe magnitude of the positive pulses exceed that of the negative ones,the pointer 29 deflects to the right of center to an extent whichindicates the magnitude of the ratio between the two kinds of pulses.Similarly, a deflection to the left of center indicates that themagnitude of the negative pulses exceeds that of the positive pulses andthe magnitude of the ratio between these two kinds of pulses isindicated by the extent of the deflection to the left from center. It isalso manifest that the relative magnitudes of the positive and negativepulses which pass through the two branches of the potentiometer arecontrollable by means of slider 3| which may be moved so as to changethe resistance of the branch 50 with respect to that of the branch 49.As a consequence, for a given A. C. input reading on the A. C.milliammeter 35, the D. C. milliamrneter 21 can be made to give anydesired 5. reading over the wholescale from lettto' right by anappropriate: setting oi *sl'ider' 31m Thus, by setting theslid'en=3al'sothat the pointer it 29 is at the center or thesca'leindicating no l).0., the current flow: in element 39' is thereby balanced againstthe=current"flow inclement 40.-

In calibrating any'of the modifications of the apparatusfor use, thefluid movement" sensing (sub's'urfacea' portion of "the apparatuscomprising-case H is submerged in "a motionless fluid; suchas a stillcolumn oi drilling-mud, so as to bring-"the elements 39 andr40' intocontact with the fluid. A; C.-issupplied to the auto-transformer 31 andslider 36 is then moved to a position 'in=whichthe A; C.milliammeter--35 shows a deflection cor-responding to about 75 per *centof its full scalereading. Slider--31 is moved until aposition is found'at which theDf'Cimilliammeter pointer 29*moves-to the extremeleftof thescale.-- ln 'thisposition, once theslidersil and 3B havebeen set, asdescribed; and the elements 39 and 46 are in contact with the motionlessambient fluid, the extreme leftreading of the D. C. milliammeter istaken as indicating absence of fluid flow relative to the elements 39and 40. The next step in the calibration is to movethe case Hof theapparatus relative to the'ambient fluid at a known rate, such as 100feet per-minute. This causes-the temperature of the elements 39 and'*4"todecrease, the one relatively more, than the-otherand; therefore, the"resistance of "the one-decreases relatively more than that of theother; As a consequence-the ratio of the mag n-itude' of the positivepulses to that of the 'negative ones is increased and this isevidencedby the pointer 29 movingto'a' position toward the right of thebeginning, or extreme left, of the scale. The slider 36is then furtheradjusted,

while the case ll of the apparatus is moved relativelyto the ambientfluid at the aforesaid known rate,'until a position for slider 36 isfound at which the pointer 29. moves to the extremeright end of thescale. a

It will be also evident that when the ambient fluidsisunot moving withrespect to the subsurface portion of the apparatus, the; D. C.milliammeter pointerwillf remain, stationary forany iven-setting of theslider 3|, and that, if the resistances of elements 39 and 40 changeequally at the same time, as when their temperatures simultaneouslychange an equal amount, the D. C. milliammeter 21 will show no change incurrent while there will be a change in the reading of the milliammetercorresponding to the increase or decrease in A. 0. input which resultsfrom the decrease or increase respectively of the temperature of the tworesistance elements, 39 and 40. By the foregoing calibration, it is thusapparent that the movement of fluid relative to the two elements, 39 and4B, is detected as a change in the D. C. milliammeter reading and achange in temperature of the ambient fluid not accompanied by movementof the ambient fluid with respect to the subsurface apparatus will bedetected as a change in the A. C. milliammeter reading without asignificant change in the D. C. milliammeter reading.

It will be apparent to those skilled in the art that variousmodifications may be made in the apparatus without departing from thescope of the invention as defined in the appended claims. For instance,the adjustable auto-transformer 37 may be omitted and the A. C. source38 connected directly to the A. C. milliammeter 35, as indicated by thedotted line 5|. The source 38 of a enine A. Cikitself could be:adjustable as to the voltage and bument of its z output; Control of theA. 0. output from the source also couldtbeeffebtedwith a rheostat (notshown)- which could be included in the-lead 5-1.

In locating a "thief zone, e; g. 2 Fig. the calibratedsubsurface-portionof the apparatus; i-. -'e.- that comprising case H in any of' itsmodifloationa is lowered into the well having a-fluid column thereince;gsdrillingmud l thetop 52" of which *ismaintained constant as to elevationby introducing mud fluid through "pipe: '6 at a suitable constant rate.On reachingthe-bottom of 'thebore of the well "the D; C; milliammeterwill deflecttotheextreme left indicating therebythat thereis nofluidflow 'relative to elements 39 and 48:" The case l l is then raised'ashort distance the mud 'column while keeping a record: oi the depthof--the--case hymeans-of the footage indi-a cater "2 0.- The readingsof'the 'D." C; milliammeter isnoted at-'-the"new depth, and, itsubstantially different from that at the bottom, this is -an inaclicatiom that a thief zone has been encountered. Iny'Figz 1,} forexampleg the case I isshown raised meterzl'. Thusby raisin the case H ashort dis;

tance at atime, no in thewreading ofithefDg. C, milliammeter at each,elevation to which the case is raised, and held at a, specificelevation, the elevation-at whichtheiflow. of. the mud flu d pafitthe-casechangfisis; ascertainedthereby revealing the elevation of a;thief zone.

I claim: 1 mnanparatus fo de e i r h wmor n of: aid in aww ll holecomprs neqa u d isht case wadapted: to :be positioned; in a column. offluidimthewell; a cable for suspending-thecase mane .iwellz. saidcablecomnr s rls 1a -sing: .e= sulated conductor and a metallic sheaththerefor; two thermally sensitive electrical resistance heating elementsone having a greater surface area than the other mounted on andinsulated from the case in position to be contacted by the fluid of thecolumn whereby a flow of fluid past the heating elements changes thetemperature and consequently the electrical resistance of one more thanthe other; means for supplying heating current to each of the heatingelements through the said insulated conductor, said means for supplyingheating current comprising an above ground source of A. C. and half-waverectifier means both above ground and in the case for directing thepositive pulses of the A. C. through only one of the two heatingelements and the negative pulses only through the other; a voltagedivider having its end terminals connected with the above groundone-half wave rectifier means and its movable terminal connected to therectifier means in the case, said voltage divider being capable ofchanging the ratio of the magnitude of the positive pulses to themagnitude of the negative pulses to a predetermined value whereby achange in the ratio is indicative of a greater change of resistance ofone of the two heating elements compared to that of the other; and D. C.current measuring means conaceas'm I! nected in series with the saidmovable terminal and the half-Wave rectifier means in the case forindicating the said ratio.

2. An apparatus for detecting the movement of fluid in a well holecomprising a fluid-tight case adapted to be positioned. in a column offluid in the well; a cable for suspending the case in the well, saidcable comprising a single insulated conductor and a metallic sheaththerefor; a reel for the cable, one end of the cable being wound on thereel and the other secured to the case with the metallic sheathconnected to the case and the insulated conductor extending into thecase; two thermally sensitive electrical resistance heatin elements onehaving a greater surface area than the other mounted on and insulatedfrom the case in position to be contacted by the fluid of the column;means for supplying heating current to each heating element through thesaid insulated conductor, said means for supplying heating currentcomprising an above ground source of A. C. and half-wave rectifier meansboth above ground and in the case for directing the positive pulses ofthe A. C. through only one of the two heating elements and the negativepulses only through the other; a voltage divider having its endterminals associated with theabove ground one-half wave rectifier meansand its movable terminal connected to the rectifier means in the case,said voltage divider being capable of changing the ratio of themagnitude of the positive pulses to the magnitude of the negative pulsesto a predetermined value whereby a change in the ratio is indicative ofa greater change. of resistance of one of the two heating elementscompared to that of the other; D. 0. current measuring means connectedin series with the said movable terminal and the half-wave rectifiermeans in the case for indicating the said ratio; and A. C. currentmeasuring means connected in series with the source of A. C. and thefirst pair of half-wave rectifiers for indicating the magnitude of theA. C. supplied.

3. Apparatus for detecting the movement of fluid in a well holecomprising an above ground source of single phase A. 0., having meansfor adjusting its magnitude; a first pair of half-wave rectifiers, thepositive terminal of one of them being connected to the negativeterminal of the other and to the input source 0! A. C. so as to separatethe positive and negative pulses of the said A. C.; a potentiometermeans having one end connected to the output of one of the said pair ofrectifiers and the other end connected to the output of the otherrectifier, the potentiometer means having an adjustable contact inter-.mediate its ends so as to permit adjustment of the magnitude of thepositive pulses of the A. C. relative to that of the negative pulses ofthe A. C.; a fluid-tight case adapted to be lowered into the fluid inthe well; two temperature sensitive electrical resistances one having agreater surface area than the other mounted in space relation to eachother on and insulated from the case; a second pair of half-waverectifiers, said second pair being mounted within the case; a cablemeans for suspending the case in the well comprising a single insulatedconductor and metallic sheath therefor, said case being secured to oneend of the cable and connected to the sheath, the insulated conductorhaving one end terminating inside the case and connected to the saidsecond pair of rectifiers and the other end above ground and connectedto the adjustable contact of the said potentiometer, the said secondpair of rectiflers being coupled to the said resistors so as topermitpulses of only one polarity to reach one of the electrical resistancesand pulses of the opposite polarity to reach only the other of theelectrical resistances; a direct current measuring means connected inseries with the single insulated conductor for indicating the ratio ofthe magnitude of the positive and negative pulses traversing theconductor; and alternating current measuring means connected in serieswith the source of A. C. and the first pair of half-wave rectifiers formeasuring the magnitude of the A. C. fed to the first pair ofrectifiers,

DALE G. HAR'IWIEIG.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,524,150 Vincent Oct. 3, 1950 2,580,182 Morgan et al Dec. 25,1951

